Despite admittedly being streaky, Schoop came into this season with his last 1200 PA at >750 OPS, there was no reason to think he was going to crash like this. Looking through all his peripherals and maybe in hindsight you can argue his pull rate and ISO were down some last season, but could have also argued that was adjustment to COPA. He had had 4 out of 5 RC+>100 seasons. I don't think it's fair to criticize the Tiger FO for thinking Schoop would again be at least in the 1-1.5 WAR range.
But given that, should we have expected Paredes to have become better than that? Before this season, if you had asked in my totally fan based subjective judgment I'd have pegged Paredes as maybe as topping out as a 2 WAR player, partly because even if the good plate discipline started to come through, he had yet to prove much in the way of his defensive chops and he does look like he could easily "grow" out of his quickness, even if he hasn't yet. Whereas I do think Schoop is a plus 2B. So sort of a wash between the two of them potential wise to me there, though of course you gain 6 yrs with Paredes.
OTOH - to me Candy's resume has been more up and down and he's missed more injury time. Even though Candy's best last year was a lot better than Schoop, to me there has always been more an aura of fragility around his performance. I don't think I would have banked on Candelario blocking anyone long term.